1 /* ====================================================================
2 * Copyright (c) 2014 The OpenSSL Project. All rights reserved.
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5 * modification, are permitted provided that the following conditions
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9 * notice, this list of conditions and the following disclaimer.
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13 * the documentation and/or other materials provided with the
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18 * "This product includes software developed by the OpenSSL Project
19 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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32 * "This product includes software developed by the OpenSSL Project
33 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
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47 * ====================================================================
51 #include <openssl/crypto.h>
52 #include "modes_lcl.h"
55 unsigned char *chrblk;
60 * Calculate the number of binary trailing zero's in any given number
62 static u32 ocb_ntz(u64 n)
67 * We do a right-to-left simple sequential search. This is surprisingly
68 * efficient as the distribution of trailing zeros is not uniform,
69 * e.g. the number of possible inputs with no trailing zeros is equal to
70 * the number with 1 or more; the number with exactly 1 is equal to the
71 * number with 2 or more, etc. Checking the last two bits covers 75% of
72 * all numbers. Checking the last three covers 87.5%
82 * Shift a block of 16 bytes left by shift bits
84 static void ocb_block_lshift(OCB_BLOCK *in, size_t shift, OCB_BLOCK *out)
86 unsigned char shift_mask;
88 unsigned char mask[15];
96 shift_mask <<= (8 - shift);
97 for (i = 15; i >= 0; i--) {
99 mask[i - 1] = locin.chrblk[i] & shift_mask;
100 mask[i - 1] >>= 8 - shift;
102 locout.chrblk[i] = locin.chrblk[i] << shift;
105 locout.chrblk[i] ^= mask[i];
111 * Perform a "double" operation as per OCB spec
113 static void ocb_double(OCB_BLOCK *in, OCB_BLOCK *out)
123 * Calculate the mask based on the most significant bit. There are more
124 * efficient ways to do this - but this way is constant time
126 mask = locin.chrblk[0] & 0x80;
130 ocb_block_lshift(in, 1, out);
132 locout.chrblk[15] ^= mask;
136 * Perform an xor on in1 and in2 - each of len bytes. Store result in out
138 static void ocb_block_xor(const unsigned char *in1,
139 const unsigned char *in2, size_t len,
143 for (i = 0; i < len; i++) {
144 out[i] = in1[i] ^ in2[i];
149 * Lookup L_index in our lookup table. If we haven't already got it we need to
152 static OCB_BLOCK *ocb_lookup_l(OCB128_CONTEXT * ctx, size_t index)
154 if (index <= ctx->l_index) {
155 return ctx->l + index;
158 /* We don't have it - so calculate it */
160 if (ctx->l_index == ctx->max_l_index) {
161 ctx->max_l_index *= 2;
162 ctx->l = OPENSSL_realloc(ctx->l, ctx->max_l_index * sizeof(OCB_BLOCK));
166 ocb_double(ctx->l + (index - 1), ctx->l + index);
168 return ctx->l + index;
172 * Encrypt a block from |in| and store the result in |out|
174 static void ocb_encrypt(OCB128_CONTEXT *ctx, OCB_BLOCK *in, OCB_BLOCK *out, void *keyenc)
182 ctx->encrypt(locin.chrblk, locout.chrblk, keyenc);
186 * Decrypt a block from |in| and store the result in |out|
188 static void ocb_decrypt(OCB128_CONTEXT *ctx, OCB_BLOCK *in, OCB_BLOCK *out, void *keydec)
196 ctx->decrypt(locin.chrblk, locout.chrblk, keydec);
200 * Create a new OCB128_CONTEXT
202 OCB128_CONTEXT *CRYPTO_ocb128_new(void *keyenc, void *keydec,
203 block128_f encrypt, block128_f decrypt)
205 OCB128_CONTEXT *octx;
208 if ((octx = (OCB128_CONTEXT *) OPENSSL_malloc(sizeof(OCB128_CONTEXT)))) {
209 ret = CRYPTO_ocb128_init(octx, keyenc, keydec, encrypt, decrypt);
219 * Initialise an existing OCB128_CONTEXT
221 int CRYPTO_ocb128_init(OCB128_CONTEXT *ctx, void *keyenc, void *keydec,
222 block128_f encrypt, block128_f decrypt)
224 /* Clear everything to NULLs */
225 memset(ctx, 0, sizeof(*ctx));
228 ctx->max_l_index = 1;
229 ctx->l = OPENSSL_malloc(ctx->max_l_index * 16);
234 * We set both the encryption and decryption key schedules - decryption
235 * needs both. Don't really need decryption schedule if only doing
236 * encryption - but it simplifies things to take it anyway
238 ctx->encrypt = encrypt;
239 ctx->decrypt = decrypt;
240 ctx->keyenc = keyenc;
241 ctx->keydec = keydec;
243 /* L_* = ENCIPHER(K, zeros(128)) */
244 ocb_encrypt(ctx, &ctx->l_star, &ctx->l_star, ctx->keyenc);
246 /* L_$ = double(L_*) */
247 ocb_double(&ctx->l_star, &ctx->l_dollar);
249 /* L_0 = double(L_$) */
250 ocb_double(&ctx->l_dollar, ctx->l);
256 * Copy an OCB128_CONTEXT object
258 int CRYPTO_ocb128_copy_ctx(OCB128_CONTEXT * dest, OCB128_CONTEXT * src,
259 void *keyenc, void *keydec)
261 memcpy(dest, src, sizeof(OCB128_CONTEXT));
263 dest->keyenc = keyenc;
265 dest->keydec = keydec;
267 dest->l = OPENSSL_malloc(src->max_l_index * 16);
270 memcpy(dest->l, src->l, (src->l_index + 1) * 16);
276 * Set the IV to be used for this operation. Must be 1 - 15 bytes.
278 int CRYPTO_ocb128_setiv(OCB128_CONTEXT * ctx, const unsigned char *iv,
279 size_t len, size_t taglen)
281 unsigned char ktop[16], tmp[16], mask;
282 unsigned char stretch[24], nonce[16];
283 size_t bottom, shift;
286 offset.ocbblk = &ctx->offset;
289 * Spec says IV is 120 bits or fewer - it allows non byte aligned lengths.
290 * We don't support this at this stage
292 if ((len > 15) || (len < 1) || (taglen > 16) || (taglen < 1)) {
296 /* Nonce = num2str(TAGLEN mod 128,7) || zeros(120-bitlen(N)) || 1 || N */
297 nonce[0] = ((taglen * 8) % 128) << 1;
298 memset(nonce + 1, 0, 15);
299 memcpy(nonce + 16 - len, iv, len);
300 nonce[15 - len] |= 1;
302 /* Ktop = ENCIPHER(K, Nonce[1..122] || zeros(6)) */
303 memcpy(tmp, nonce, 16);
305 ctx->encrypt(tmp, ktop, ctx->keyenc);
307 /* Stretch = Ktop || (Ktop[1..64] xor Ktop[9..72]) */
308 memcpy(stretch, ktop, 16);
309 ocb_block_xor(ktop, ktop + 1, 8, stretch + 16);
311 /* bottom = str2num(Nonce[123..128]) */
312 bottom = nonce[15] & 0x3f;
314 /* Offset_0 = Stretch[1+bottom..128+bottom] */
316 ocb_block_lshift((OCB_BLOCK *)(stretch + (bottom / 8)), shift, &ctx->offset);
319 offset.chrblk[15] |= (*(stretch + (bottom / 8) + 16) & mask) >> (8 - shift);
325 * Provide any AAD. This can be called multiple times. Only the final time can
326 * have a partial block
328 int CRYPTO_ocb128_aad(OCB128_CONTEXT * ctx, const unsigned char *aad,
331 u64 all_num_blocks, num_blocks;
337 /* Calculate the number of blocks of AAD provided now, and so far */
338 num_blocks = len / 16;
339 all_num_blocks = num_blocks + ctx->blocks_hashed;
341 /* Loop through all full blocks of AAD */
342 for (i = ctx->blocks_hashed + 1; i <= all_num_blocks; i++) {
344 OCB_BLOCK *aad_block;
346 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
347 lookup = ocb_lookup_l(ctx, ocb_ntz(i));
350 ocb_block16_xor(&ctx->offset_aad, lookup, &ctx->offset_aad);
352 /* Sum_i = Sum_{i-1} xor ENCIPHER(K, A_i xor Offset_i) */
353 aad_block = (OCB_BLOCK *) (aad + ((i - ctx->blocks_hashed - 1) * 16));
354 ocb_block16_xor(&ctx->offset_aad, aad_block, &tmp1);
355 ocb_encrypt(ctx, &tmp1, &tmp2, ctx->keyenc);
356 ocb_block16_xor(&ctx->sum, &tmp2, &ctx->sum);
360 * Check if we have any partial blocks left over. This is only valid in the
361 * last call to this function
366 /* Offset_* = Offset_m xor L_* */
367 ocb_block16_xor(&ctx->offset_aad, &ctx->l_star, &ctx->offset_aad);
369 /* CipherInput = (A_* || 1 || zeros(127-bitlen(A_*))) xor Offset_* */
370 memset((void *)&tmp1, 0, 16);
371 memcpy((void *)&tmp1, aad + (num_blocks * 16), last_len);
372 ((unsigned char *)&tmp1)[last_len] = 0x80;
373 ocb_block16_xor(&ctx->offset_aad, &tmp1, &tmp2);
375 /* Sum = Sum_m xor ENCIPHER(K, CipherInput) */
376 ocb_encrypt(ctx, &tmp2, &tmp1, ctx->keyenc);
377 ocb_block16_xor(&ctx->sum, &tmp1, &ctx->sum);
380 ctx->blocks_hashed = all_num_blocks;
386 * Provide any data to be encrypted. This can be called multiple times. Only
387 * the final time can have a partial block
389 int CRYPTO_ocb128_encrypt(OCB128_CONTEXT * ctx,
390 const unsigned char *in, unsigned char *out,
394 u64 all_num_blocks, num_blocks;
401 * Calculate the number of blocks of data to be encrypted provided now, and
404 num_blocks = len / 16;
405 all_num_blocks = num_blocks + ctx->blocks_processed;
407 /* Loop through all full blocks to be encrypted */
408 for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
413 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
414 lookup = ocb_lookup_l(ctx, ocb_ntz(i));
417 ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);
419 /* C_i = Offset_i xor ENCIPHER(K, P_i xor Offset_i) */
420 inblock = (OCB_BLOCK *) (in + ((i - ctx->blocks_processed - 1) * 16));
421 ocb_block16_xor(&ctx->offset, inblock, &tmp1);
422 ocb_encrypt(ctx, &tmp1, &tmp2, ctx->keyenc);
424 (OCB_BLOCK *) (out + ((i - ctx->blocks_processed - 1) * 16));
425 ocb_block16_xor(&ctx->offset, &tmp2, outblock);
427 /* Checksum_i = Checksum_{i-1} xor P_i */
428 ocb_block16_xor(&ctx->checksum, inblock, &ctx->checksum);
432 * Check if we have any partial blocks left over. This is only valid in the
433 * last call to this function
438 /* Offset_* = Offset_m xor L_* */
439 ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);
441 /* Pad = ENCIPHER(K, Offset_*) */
442 ocb_encrypt(ctx, &ctx->offset, &pad, ctx->keyenc);
444 /* C_* = P_* xor Pad[1..bitlen(P_*)] */
445 ocb_block_xor(in + (len / 16) * 16, (unsigned char *)&pad, last_len,
446 out + (num_blocks * 16));
448 /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
449 memset((void *)&tmp1, 0, 16);
450 memcpy((void *)&tmp1, in + (len / 16) * 16, last_len);
451 ((unsigned char *)(&tmp1))[last_len] = 0x80;
452 ocb_block16_xor(&ctx->checksum, &tmp1, &ctx->checksum);
455 ctx->blocks_processed = all_num_blocks;
461 * Provide any data to be decrypted. This can be called multiple times. Only
462 * the final time can have a partial block
464 int CRYPTO_ocb128_decrypt(OCB128_CONTEXT * ctx,
465 const unsigned char *in, unsigned char *out,
469 u64 all_num_blocks, num_blocks;
475 * Calculate the number of blocks of data to be decrypted provided now, and
478 num_blocks = len / 16;
479 all_num_blocks = num_blocks + ctx->blocks_processed;
481 /* Loop through all full blocks to be decrypted */
482 for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
486 /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
487 OCB_BLOCK *lookup = ocb_lookup_l(ctx, ocb_ntz(i));
490 ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);
492 /* P_i = Offset_i xor DECIPHER(K, C_i xor Offset_i) */
493 inblock = (OCB_BLOCK *) (in + ((i - ctx->blocks_processed - 1) * 16));
494 ocb_block16_xor(&ctx->offset, inblock, &tmp1);
495 ocb_decrypt(ctx, &tmp1, &tmp2, ctx->keydec);
496 outblock = (OCB_BLOCK *) (out + ((i - ctx->blocks_processed - 1) * 16));
497 ocb_block16_xor(&ctx->offset, &tmp2, outblock);
499 /* Checksum_i = Checksum_{i-1} xor P_i */
500 ocb_block16_xor(&ctx->checksum, outblock, &ctx->checksum);
504 * Check if we have any partial blocks left over. This is only valid in the
505 * last call to this function
510 /* Offset_* = Offset_m xor L_* */
511 ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);
513 /* Pad = ENCIPHER(K, Offset_*) */
514 ocb_encrypt(ctx, &ctx->offset, &pad, ctx->keyenc);
516 /* P_* = C_* xor Pad[1..bitlen(C_*)] */
517 ocb_block_xor(in + (len / 16) * 16, (unsigned char *)&pad, last_len,
518 out + (num_blocks * 16));
520 /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
521 memset((void *)&tmp1, 0, 16);
522 memcpy((void *)&tmp1, out + (len / 16) * 16, last_len);
523 ((unsigned char *)(&tmp1))[last_len] = 0x80;
524 ocb_block16_xor(&ctx->checksum, &tmp1, &ctx->checksum);
527 ctx->blocks_processed = all_num_blocks;
533 * Calculate the tag and verify it against the supplied tag
535 int CRYPTO_ocb128_finish(OCB128_CONTEXT * ctx, const unsigned char *tag,
538 OCB_BLOCK tmp1, tmp2;
540 /*Tag = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) xor HASH(K,A) */
541 ocb_block16_xor(&ctx->checksum, &ctx->offset, &tmp1);
542 ocb_block16_xor(&tmp1, &ctx->l_dollar, &tmp2);
543 ocb_encrypt(ctx, &tmp2, &tmp1, ctx->keyenc);
544 ocb_block16_xor(&tmp1, &ctx->sum, &ctx->tag);
546 if (len > 16 || len < 1) {
550 /* Compare the tag if we've been given one */
552 return CRYPTO_memcmp(&ctx->tag, tag, len);
558 * Retrieve the calculated tag
560 int CRYPTO_ocb128_tag(OCB128_CONTEXT * ctx, unsigned char *tag, size_t len)
562 if (len > 16 || len < 1) {
566 /* Calculate the tag */
567 CRYPTO_ocb128_finish(ctx, NULL, 0);
569 /* Copy the tag into the supplied buffer */
570 memcpy(tag, &ctx->tag, len);
576 * Release all resources
578 void CRYPTO_ocb128_cleanup(OCB128_CONTEXT * ctx)
582 OPENSSL_cleanse(ctx->l, ctx->max_l_index * 16);
583 OPENSSL_free(ctx->l);
585 OPENSSL_cleanse(ctx, sizeof(*ctx));